The invention relates generally to the field of electrical enclosures, such as enclosures for motor control centers used in industrial and commercial settings. More particularly, embodiments of the present invention relate to electrical enclosures designed with arc resistant features.
Electrical enclosures and cabinets can be used in a wide range of industrial and automation applications. In general, electrical enclosures typically include a shell or box made of a heavy gauge sheet metal. The enclosures are configured to support electrical circuitry and electrical components therein, and to receive and send electrical power and data signals. The enclosures may include both small and large individual units, such as for housing components, such as contactors and other switches. Further, larger enclosures can be employed to house various power electronics equipment, control circuits, motor drives, and so forth. For example, in industry it is common to find large enclosures divided into bays or segments for single and three-phase switches, motor controllers, programmable logic controllers, data and power network interfaces, and so forth.
A particular challenge in the design and operation of electrical components in enclosures relates to designing the enclosures to withstand the mechanical and thermal effects of an internal arcing fault (also called an arc, arc fault, arc flash, arcing flash, etc.). For example, certain types of electrical faults can produce arcs that can heat and even vaporize neighboring components and cause sudden pressure increases and localized overheating. While development of protective circuitry has focused on interrupting such faults extremely quickly, even a few cycles of alternating current can suffice to vaporize wires, insulation, and even component housings. Such faults can result in volumes of hot gas that expand and must be channeled and/or vented within or from the enclosure. Further, the faults can produce high temperatures and pressure increases that cause mechanical and thermal stresses on the electrical enclosures. Arcing faults can cause damage to equipment and facilities and increase costs due to lost production. Accordingly, industrial standards and guides have been developed as a way for manufacturers to demonstrate that the electrical enclosures can withstand the mechanical and thermal effects of an internal arcing fault.